1. Field of the Invention
This invention refers to the field of plant protection, and especially to the determining of the actual amount of plant protective substances sprayed by spraying machines.
2. Description of the Prior Art
DE-AS No. 16 07 391, DE-OS No. 25 55 011, Periodical Agrartechnik International, February 80, page 32.
For discharging plant protective substances in agriculture plant protective spraying machines are used. For the spraying which is carried out over wide areas from vehicles on the ground, so-called area spraying lever systems are used which are provided with pipes arranged transversely to the direction in which the vehicle moves, which are different widths (about 6-24 m), and on which a plurality of nozzles are mounted for discharging the protective substances. These nozzles usually are arranged at a distance of 50 cm from each other. Because the plant protective substances, which are usually diluted in an aqueous solution, are to be sprayed in a very precise manner, plant protective spraying systems generally have metering devices which operate in a more or less exact manner and are operated manually, semi-automatically or fully-automatically. The metering data provided by the manufacturers of plant protective substances generally refer to liter per hectares (one hectare=10.000 square meters). The parameters for the amount of sprayed liquid are the speed of movement, the operating width and the amount of discharge. In view of the costs, most of the plant protective spraying machines used in practice are not provided with a metering device for measuring the speed of movement separately. The speed of movement is generally read from the speedometer of the tractor or alternatively is determined by trial and error. With equal nozzle distance of f.i. 50 cm it is not necessary to consider the entire operating width of the area spraying lever system because each nozzle sprays an identical area at an equal speed of movement. Therefore, it is sufficient to start from the discharge amount of an individual nozzle if all other nozzles are of the same type, are substantially identical, have the same degree of wear, and operate under equal pressure conditions. Most of the plant protective spraying machines used in practice are not provided with measuring means for metering the amount of liquid actually discharged by the nozzles. Therefore, in general only the discharge "pressure" is measured. By means of a discharge amount table, which is classified according to nozzle types (nozzles sizes) from the pressure, the actual discharge or the actually discharged amount in liter per hectares can be read from the pressure depending on the speed of movement. Semi-automatically operating plant protective spraying machines, and a number of the standard plant protective spraying machines, are provided with so-called adjustment aids, according to which the discharge amount table is arranged directly at or around the manometer so that from the indication on the manometer, depending on the type of nozzle used and the chosen speed of movement, the actual discharge amount can be read in liters per hectares.
However, the exactness of this measuring method depends to a considerable extent on whether the used nozzle type (nozzle size) actually rallies with the supplied table, on the actual condition (wear) of the nozzles, on the exactness of indication of the manometer, on the density and viscosity of the discharged liquid, and on any pressure losses between the measuring point of the manometer and the corresponding nozzles. Additional deviations can result from nozzle series elements, which are manually used, f.i. nozzle filters, ball valve filters, ball valves etc.
For these reasons it is necessary for the farmer to be in a position to individually check the actual discharge amount of his plant protective spraying machine before starting any spraying operation, and this is done in practice according to one of the following two methods:
Method 1.: The container of the plant protective spraying machine is filled with water to a predetermined level. Then operation of the machine is started and the machine is moved over a predetermined surface area. Subsequent thereto, the discharged amount of liquid is measured within the container (the difference in volume), and this amount is divided by the area of the surface over which the machine has been moved, and the value obtained is calculated for liters per hectares. This method has the following main error sources: Usually, the amount of liquid lacking in the container is read from the container scale, so that considerable errors occur as a result of the inexactness of the container scale, varying inclination of the container, too rough divisions of the scale, and reading errors.
Method 2.: A measuring beaker is placed underneath a nozzle for a predetermined time with a pre-set operating pressure; the discharge amount and the measuring time are predetermined; the value is calculated for liters per minute or liters per hour; and then, by means of a table or a slide rule the actually discharged amount in liters per hectares is determined for a predetermined speed of movement. The disadvantage of this method is that it is rather complicated for the farmer to carry out this method in practice.
Both methods usually require a thorough knowledge of the physical and calculating procedures as well as of the possible error sources. The ordinary farmer usually does not possess this knowledge. Futhermore, the checking methods are rather complicated and time consuming. This has led to the fact that the farmer merely checks the actual discharge values of his spraying machine--if at all--once a year before the spraying season starts, and subsequent thereto does not make any alterations in the adjustment of the spraying machine so that he sprays all the widely different substances with the same amount of liquid. Of course, the result is, that on the other hand the effect of the spraying material is considerably decreased, and that on the other hand the farmer, when mixing the various fluid concentrations, makes mistakes; or that mistakes are caused because he relies on the steady discharge amount of his spraying machine. It is not necessary to deal in detail with the ecological problems of over-and under-concentrations of plant protective substances.